I did not, but I managed to barely squeak by using demons who resist force. Even then, he still almost killed me with his stupid multi hit BS attack. Like goddamn, at one point I was down to two party members and only like ~15 hp each. Managed to bring it back though and claim g l o r i o u s v i c t o r y

I still need to play this game. I love absolutely everything about it.

That said I've watched a speedrun and they confirmed that their responses to the negotiations are random. If it's a demon you really want, and they ask for stuff, it seems like you should give them whatever they want and hope for the best.